Following a review of the recommendations from the Lower Tidal River Arun Strategy (approved in 2014) for Arundel, West Sussex, the Environment Agency has accelerated phase 1of the tidal defence scheme to reduce the risk of flooding and erosion to properties in Arundel as quickly as possible.
Following a review of the recommendations from the Lower Tidal River Arun Strategy (approved in 2014) for Arundel, West Sussex, the Environment Agency has accelerated phase 1of the tidal defence scheme to reduce the risk of flooding and erosion to properties in Arundel as quickly as possible.
The Arundel tidal defence scheme is looking to improve flood defences in areas of Arundel at highest risk - work on the scheme has already started. In 2018 the Agency conducted engineering surveys of the river defences in Arundel, including drone surveys, visual inspections, surveys of the river bed and thickness tests of sheet steel piles on the River Road side. The Agency also investigated boreholes on both sides of the river - the material below ground will help to better understand the stability of the river defences over the long-term.
Construction of new flood defences and work to strengthen the river wall will start in November 2019 and continue to February 2020 and May 2020 respectively.
Work to the embankments south of the A27 bridge is scheduled to take place between April and June 2020.
The Environment Agency anticipate the scheme will better protect:
- around 130 properties from flooding
- up to 30 properties against river erosion on both river banks.
In early 2016, the Environment Agency separately developed an Emergency Response Plan. This was for the increased flood risk presented by the failure of the flood defence (river wall) at River Road, Arundel. The emergency plan details how they will respond to high water levels in the River Arun and the increased flood risk posed to properties in the area.
In November 2018, they reviewed and updated the plan, both in readiness for winter and to ensure their approach is as effective as possible.
The Environment Agency has 3 stages to the Emergency Response Plan, which are linked to the forecast river level:
Stages 1 and 2
These actions will better protect the properties directly affected in River Road. This would involve positioning sandbags along the patio gardens. They will work with the residents to carry out this activity when necessary.
Stage 3
This would involve setting up a temporary (aluminium) flood barrier when river levels are expected to be exceptionally high. It would be placed in River Road to better protect additional properties that may be at flood risk in this area.
The Environment Agency would also work closely with the River Road residents who live between the temporary flood barrier and the river. This would involve placing sandbags along with other specialist products to better protect their properties, including covering doors and airbricks.
Preparing for an emergency
In order to understand the flood risk in the area, the Environment Agency forecasts the combination of the tidal level and the river level using modelling software. It bases its decision to respond on the information provided by this modelled forecast data.
The water level in the River Arun at Arundel is referred to as being tidally dominated, which means that the sea level is the primary factor in determining the river level. This allows the Environment Agency to accurately forecast river levels 3 days in advance of high river levels.
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